The treatment of infected open wounds has long been a troublesome area of medical practice. An initial stage of wound healing is characterized by the formation of granulation tissue, which is a matrix of collagen, fibronectin, and hyaluronic acid carrying macrophages, fibroblasts and neovasculature that forms the basis for subsequent epithelialization of the wound. Infection (including that by bacteria, mold spores, yeast, and virus) can hinder the formation of granulation tissue within the wound, thereby inhibiting healing.
Many infected wounds, and in particular those infected with bacteria, are treated with antibiotics. These therapeutic agents can be applied topically or administered via some other route, such as orally. Unfortunately, due to the constant use (and perhaps the overuse) of antibiotics, some bacteria have evolved to become resistant to antibiotics. As a result of the therapeutic failure of some front-line antibiotics, the medical community is faced with developing new patient treatment options.
It has been known for some time that ultraviolet (UV) light can have antimicrobial effects. See, e.g., Licht, Therapeutic Electricity and Ultraviolet Radiation (Waverly Press, 1967). Early experiments demonstrated that properties of sunlight (either a heating effect or a property of the sun's rays itself) could prevent bacterial growth. Later, UV light was shown to be bacteriocidal to many bacteria, including Mycobacterium tuberculosis, Staphlococcus, Streptococcus, Bacillus anthrasis, and Shigella dysenteriae. UW light has also been a common treatment for tuberculosis of the skin. Id.
UV light can be divided into different classes based on wavelength, including ultraviolet A (UVA) at about 350 nm, ultraviolet B (UVB) at about 300 nm, and ultraviolet C (UVC) at about 250 nm. Not unexpectedly, the effectiveness of UV light in producing biological changes can differ at different wavelengths.
For wound healing, the use of UV light is attractive in that it is a non-pharmalogical treatment that is non-invasive to the wound. It has been demonstrated that UV light can increase epithelial cell turnover, release prostaglandin precursors and histamines, increase vascular permeability, accelerate DNA synthesis, and inactivate bacterial cells. However, UVA and UVB have been shown to cause damage to the skin, particularly in the form of sunburn and blistering, each of which would be undesirable, particularly to an open wound; also, these forms of UV radiation have been demonstrated to be carcinogenic.